Parathion (0,0-diethyl-O-p-nitrophenyl phosphorothioate) was discovered in 1944 by Schrader (Eto, M., 1974 organophosphorus pesticides: organic and biological chemistry, CRC Press Inc., Cleveland, Ohio). It is an organophosphate pesticide that is extremely toxic to higher organisms because parathion (PAR) is converted by the cytochrome P-450 monooxygenase system to paraoxon which is a potent acetylcholinesterase inhibitor (Taylor, The pharmacological basis of therapeutics, 6th ed. pp. 100-119 (1980)).
Organophosphate pesticides applied to agricultural environments at recommended rates are not extremely persistent. However, when higher concentrations of PAR are applied to soil samples, persistence increases, and PAR can be detected in some soils after 16 years (Wolfe et al., Bull. Environ. Contam. Toxicol. 10:1-9 (1973)). It has been estimated that the remaining pesticide residue in pesticide containers is approximately 4.5.times.10.sup.5 kilograms per year (Munnecke, Process Biochem. 13:16-19 (1978)). The major source of pesticide discharges occurs at pesticide production and formulation plants, which release more than 4.times.10.sup.5 kilograms of pesticides each year (Munnecke, supra (1978)). Therefore, hazards exist with respect to undesirable discharges such as pesticide containers, production plants, or accidental spills (Munnecke, Microbial degradation of xenobiotics and recalcitrant compounds, Academic Press Inc., London, pp. 251-270 (1981)). In these instances, clean-up procedures are required. Enzymes which can decrease the toxicity of the pesticide molecule by a simple hydrolysis reaction could possibly be used for the detoxification of residual pesticides at these industrial point sources.